Fix sourceURL & sourceMapURL handling in case of background parsing

src/parser.h

Index: src/parser.h
diff --git a/src/parser.h b/src/parser.h
index 02dfe15f8ef31bdc76b978277433c62951c5d921..219f1c4b211a591ab807ce33d303e9602dafa72e 100644
--- a/src/parser.h
+++ b/src/parser.h
@@ -682,6 +682,7 @@ class Parser : public ParserBase<ParserTraits> {
   // Handle errors detected during parsing, move statistics to Isolate,
   // internalize strings (move them to the heap).
   void Internalize();
+  void HandleSourceURLComments();
 
  private:
   friend class ParserTraits;
@@ -879,8 +880,6 @@ class Parser : public ParserBase<ParserTraits> {
       const AstRawString* function_name, int pos, Variable* fvar,
       Token::Value fvar_init_op, bool is_generator, bool* ok);
 
-  void HandleSourceURLComments();
-
   void ThrowPendingError();
 
   TemplateLiteralState OpenTemplateLiteral(int pos);